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From: Thomas Gleixner <tglx@linutronix.de>
To: Fabio Estevam <festevam@gmail.com>
Cc: "Paul E . McKenney" <paulmck@kernel.org>,
	Kalle Valo <kvalo@codeaurora.org>,
	ath10k@lists.infradead.org, linux-mmc <linux-mmc@vger.kernel.org>,
	Ulf Hansson <ulf.hansson@linaro.org>, Marek Vasut <marex@denx.de>,
	qais.yousef@arm.com, Frederic Weisbecker <frederic@kernel.org>
Subject: Re: NOHZ tick-stop error with ath10k SDIO
Date: Sun, 05 Sep 2021 15:00:32 +0200	[thread overview]
Message-ID: <87y28b9nyn.ffs@tglx> (raw)
In-Reply-To: <CAOMZO5BnPEnF-HNM7vCzeUrRW7BsQ-hhm4fcVmO_QieKf6oJsw@mail.gmail.com>

Fabio,

On Sat, Sep 04 2021 at 18:10, Fabio Estevam wrote:
> On Fri, Sep 3, 2021 at 5:07 AM Thomas Gleixner <tglx@linutronix.de> wrote:
> I did as suggested and here is trace.txt:
> https://pastebin.com/VUfLRJ8a

Lacks a stack trace, but yes this one is the culprit:

kworker/u4:2-70      [000] d..1    87.940929: softirq_raise: vec=3 [action=NET_RX]

It has only interrupts and preemption disabled and it's in task
context. So if there is no interrupt raised and no local_bh_disable /
enable() pair invoked before the CPU goes idle nothing will handle the
softirq and the raised bit stays pending which makes the NOHZ idle code
complain.

> Also, while investigating this problem I saw a commit that fixed a
> similar issue:
> e63052a5dd3c ("mlx5e: add add missing BH locking around napi_schdule()").
>
> I then tried the same approach on the ath10k sdio driver:
>
> diff --git a/drivers/net/wireless/ath/ath10k/sdio.c
> b/drivers/net/wireless/ath/ath10k/sdio.c
> index b746052737e0..eb705214f3f0 100644
> --- a/drivers/net/wireless/ath/ath10k/sdio.c
> +++ b/drivers/net/wireless/ath/ath10k/sdio.c
> @@ -1363,8 +1363,11 @@ static void
> ath10k_rx_indication_async_work(struct work_struct *work)
>          ep->ep_ops.ep_rx_complete(ar, skb);
>      }
>
> -    if (test_bit(ATH10K_FLAG_CORE_REGISTERED, &ar->dev_flags))
> +    if (test_bit(ATH10K_FLAG_CORE_REGISTERED, &ar->dev_flags)) {
> +        local_bh_disable();
>          napi_schedule(&ar->napi);
> +        local_bh_enable();
> +    }
>  }
>
> and no longer get the "NOHZ tick-stop error: Non-RCU local softirq work is
> pending, handler #08!!!" error messages after launching hostapd.
>
> Is this a proper fix?

Yes. This is correct. See above.

Thanks,

        tglx

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  reply	other threads:[~2021-09-05 13:00 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18 15:18 Fabio Estevam
2021-08-18 15:43 ` Paul E. McKenney
2021-08-18 16:29   ` Fabio Estevam
2021-08-18 17:02     ` Fabio Estevam
2021-08-18 17:56       ` Paul E. McKenney
2021-08-19 13:24         ` Fabio Estevam
2021-09-02 21:51         ` Thomas Gleixner
2021-09-02 22:09           ` Paul E. McKenney
2021-09-03  8:07           ` Thomas Gleixner
2021-09-04 21:10             ` Fabio Estevam
2021-09-05 13:00               ` Thomas Gleixner [this message]
2021-09-05 13:07                 ` Fabio Estevam
2021-09-17 16:32   ` Qais Yousef
2021-09-17 17:09     ` Paul E. McKenney

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